International Numbering Plans
A collection of all international numbering plans in the world. Some features require a paid subscription.
http://www.numberingplans.com/
http://www.numberingplans.com/
Area Code Information
Detailed information on the history and current developments in North American NPA allocations.
Number Portability
Collates information on the regional initiatives in place to develop number portability and number pooling in the US.
The Telephone Exchange Name Project
The historical relationship between North American telephone exchange names and numbers.
http://ourwebhome.com/TENP/TENproject.html
http://ourwebhome.com/TENP/TENproject.html